Useful links for natbib package

(1) Natbib reference sheet

- http://mirror.unl.edu/ctan/macros/latex/contrib/natbib/natnotes.pdf

(2) Issue with Springer spbasic

- http://tex.stackexchange.com/questions/75182/issue-with-springer-spbasic

Squeezing Space from Latex

http://www.eng.cam.ac.uk/help/tpl/textprocessing/squeeze.html